In order to reduce the amount of information that needs to be transmitted television broadcast formats use an interlaced video signal. In an interlace video signal format only half the lines that comprise full image are transmitted during each scan field. Thus, during each scan of the television screen, every other scan line is transmitted. Specifically, first the odd scan lines are transmitted and then the even scan lines are transmitted in an alternating fashion. The two fields are interlaced together to construct a full video frame. In the American National Television Standards Committee (NTSC) television format, each field is transmitted in one sixtieth of a second. Thus, a full video frame (an odd field and an even field) is transmitted each one thirtieth of a second.
Computer monitors do not use the interlace video format. Instead, computer monitors use a progressive format where an entire video image is drawn in a single frame scan. Thus, during each frame scan of the monitor, every scan line is refreshed.
In order to display an interlaced television signal on a non-interlaced computer monitor the interlace video signal must be de-interlaced. De-interlacing consist of filling in the missing even or odd scan lines in each field such that each field becomes a full video frame. The process of creating the missing odd or even scan lines for the even or odd fields respectively is referred to as line-doubling.
The video recording, video editing, and video display have become popular applications of computer systems. Since video applications have become so important, high quality video de-interlacing techniques are needed.